Cascode circuit and semiconductor device

Abstract

A reference voltage circuit having a high power supply rejection ratio, and can operate at low voltage is provided. The reference voltage circuit includes a bias circuit constructed such that a depletion type transistor ( 3 ) is connected in series to a power supply voltage supply terminal of a load circuit, an enhancement type MOS transistor ( 4 ) for detecting current through the load circuit to operate as a current source is connected to the load circuit, a depletion type MOS transistor ( 5 ) is connected in series to the transistor ( 4 ), and a gate terminal of the transistor ( 5 ) is connected to a source terminal of the transistor ( 5 ), in which the gate terminal of the depletion type transistor ( 3 ) is connected to the source terminal of the depletion type transistor ( 5 ).

1. A cascode circuit comprising:
 a first N-channel depletion type MOS transistor having a source and a gate connected to each other; 
 a second N-channel depletion type MOS transistor having a gate connected to the gate of the first N-channel depletion type MOS transistor, for supplying power to a load circuit connected to a source of the second N-channel depletion type MOS transistor; and 
 a control current source connected to the source of the first N-channel depletion type MOS transistor, the control current source being controlled by current through the load circuit, wherein 
 the drain-source voltage of the first N-channel depletion type MOS transistor is set to be higher than threshold voltage, and the substrate potential is set to be lower than source potential of the first N-channel depletion type MOS transistor, and 
 the drain-source voltage of the second N-channel depletion type MOS transistor is set to be higher than threshold voltage, and the substrate potential is set to be lower than source potential of the second N-channel depletion type MOS transistor. 
 
   
   
     2. A cascode circuit according to  claim 1 , wherein the substrate potential of the first N-channel depletion type MOS transistor and the substrate potential of the second N-channel depletion type MOS transistor are grounded. 
   
   
     3. A cascode circuit according to  claim 1 , wherein the control current source comprises a first N-channel enhancement type MOS transistor having a gate connected to the load circuit and having a drain connected to the source of the first N-channel depletion type MOS transistor. 
   
   
     4. A semiconductor device comprising the cascode circuit according to  claim 3 , wherein the load circuit is a reference voltage circuit comprising:
 a third N-channel depletion type MOS transistor having a drain connected to the source of the second N-channel depletion type MOS transistor and having a source and a gate connected to the gate of the first N-channel enhancement type type MOS transistor; and 
 a second N-channel enhancement type MOS transistor having a drain and a gate connected to the source of the third N-channel depletion type MOS transistor. 
 
   
   
     5. A semiconductor device comprising the cascode circuit according to  claim 3 , wherein the load circuit is a source follower circuit comprising:
 a third N-channel enhancement type MOS transistor having a drain connected to the source of the second N-channel depletion type MOS transistor; and 
 a second N-channel enhancement type MOS transistor having a drain and a gate connected to the source of the third N-channel enhancement type MOS transistor and to the gate of the first N-channel enhancement type MOS transistor. 
 
   
   
     6. A semiconductor device according to  claim 4 , wherein the transconductance coefficient of the first N-channel enhancement type MOS transistor is made larger than the transconductance coefficient of the second N-channel enhancement type MOS transistor. 
   
   
     7. A semiconductor device according to  claim 4 , wherein the transconductance coefficient of the first N-channel depletion type MOS transistor is made smaller than the transconductance coefficient of the second N-channel depletion type MOS transistor. 
   
   
     8. A semiconductor device according to  claim 4 , wherein
 the transconductance coefficient of the first N-channel enhancement type MOS transistor is made larger than the transconductance coefficient of the second N-channel enhancement type MOS transistor, and 
 the transconductance coefficient of the first N-channel depletion type MOS transistor is made smaller than the transconductance coefficient of the second N-channel depletion type MOS transistor. 
 
   
   
     9. A semiconductor device according to  claim 5 , wherein the transconductance coefficient of the first N-channel enhancement type MOS transistor is made larger than the transconductance coefficient of the second N-channel enhancement type MOS transistor. 
   
   
     10. A semiconductor device according to  claim 5 , wherein the transconductance coefficient of the first N-channel depletion type MOS transistor is made smaller than the transconductance coefficient of the second N-channel depletion type MOS transistor. 
   
   
     11. A semiconductor device according to  claim 5 , wherein
 the transconductance coefficient of the first N-channel enhancement type MOS transistor is made larger than the transconductance coefficient of the second N-channel enhancement type MOS transistor, and 
 the transconductance coefficient of the first N-channel depletion type MOS transistor is made smaller than the transconductance coefficient of the second N-channel depletion type MOS transistor. 
 
   
   
     12. A semiconductor device comprising a cascode circuit, the cascode circuit comprising:
 a first N-channel depletion type MOS transistor having a source and a gate connected to each other; 
 a second N-channel depletion type MOS transistor having a gate connected to the gate of the first N-channel depletion type MOS transistor; 
 a third N-channel depletion type MOS transistor having a drain connected to a source of the second N-channel depletion type MOS transistor, and having a source and a gate connected to each other; 
 a second N-channel enhancement type MOS transistor having a drain connected to the source of the third N-channel depletion type MOS transistor; 
 a first N-channel enhancement type MOS transistor having a drain connected to the source of the first N-channel depletion type MOS transistor; 
 a fourth N-channel depletion type MOS transistor having a gate connected to the gate of the first N-channel depletion type MOS transistor; 
 a fifth N-channel depletion type MOS transistor having a drain connected to a source of the fourth N-channel depletion type MOS transistor, and having a gate connected to the source of the third N-channel depletion type MOS transistor; and 
 a plurality of serially connected resistances connected to the gates of the first and second N-channel enhancement type MOS transistors and to a source of the fifth N-channel depletion type MOS transistor, wherein 
 the cascode circuit is constructed such that positive constant voltage is output from an arbitrary point of connection of the plurality of serially connected resistances, and 
 substrate potentials of all the MOS transistors are grounded. 
 
   
   
     13. A semiconductor device according to  claim 12 , wherein the transconductance coefficient of the first N-channel enhancement type MOS transistor is made larger than the transconductance coefficient of the second N-channel enhancement type MOS transistor. 
   
   
     14. A semiconductor device according to  claim 12 , wherein the transconductance coefficient of the first N-channel depletion type MOS transistor is made smaller than the transconductance coefficient of the second N-channel depletion type MOS transistor. 
   
   
     15. A semiconductor device according to  claim 12 , wherein
 the transconductance coefficient of the first N-channel enhancement type MOS transistor is made larger than the transconductance coefficient of the second N-channel enhancement type MOS transistor, and 
 the transconductance coefficient of the first N-channel depletion type MOS transistor is made smaller than the transconductance coefficient of the second N-channel depletion type MOS transistor. 
 
   
   
     16. A semiconductor device comprising a cascode circuit, the cascode circuit comprising:
 a first N-channel depletion type MOS transistor having a source and a gate connected to each other; 
 a second N-channel depletion type MOS transistor having a gate connected to the gate of the first N-channel depletion type MOS transistor; 
 a third N-channel depletion type MOS transistor having a drain connected to a source of the second N-channel depletion type MOS transistor, and having a source and a gate connected to each other; 
 a second N-channel enhancement type MOS transistor having a drain connected to the source of the third N-channel depletion type MOS transistor; 
 a first N-channel enhancement type MOS transistor having a drain connected to the source of the first N-channel depletion type MOS transistor; 
 a fourth N-channel depletion type MOS transistor having a gate connected to the gate of the second N-channel depletion type MOS transistor; 
 a fifth N-channel depletion type MOS transistor having a drain connected to a source of the fourth N-channel depletion type MOS transistor, and having a gate connected to the source of the third N-channel depletion type MOS transistor; and 
 a plurality of serially connected resistances connected to the gates of the first and second N-channel enhancement type MOS transistors and to a source of the fifth N-channel depletion type MOS transistor, wherein 
 the cascode circuit is constructed such that positive constant voltage is output from an arbitrary point of connection of the plurality of serially connected resistances, and 
 substrate potentials of all the MOS transistors are grounded. 
 
   
   
     17. A semiconductor device according to  claim 16 , wherein the transconductance coefficient of the first N-channel enhancement type MOS transistor is made larger than the transconductance coefficient of the second N-channel enhancement type MOS transistor. 
   
   
     18. A semiconductor device according to  claim 16 , wherein the transconductance coefficient of the first N-channel depletion type MOS transistor is made smaller than the transconductance coefficient of the second N-channel depletion type MOS transistor. 
   
   
     19. A semiconductor device according to  claim 16 , wherein
 the transconductance coefficient of the first N-channel enhancement type MOS transistor is made larger than the transconductance coefficient of the second N-channel enhancement type MOS transistor, and 
 the transconductance coefficient of the first N-channel depletion type MOS transistor is made smaller than the transconductance coefficient of the second N-channel depletion type MOS transistor.